Electrical apparatus and core therefor



April 5. 1927; 1,623,345

N. M. HOPKINS- ELECTRICAL Armuujs AND com: THEREFOR Filed Feb.18. 1921 ATTgRNEYg.

Patented Apr. 5, 192;

UNITED sires rrENroFFIcE.

NEVIL MONROE HOPKINS, OF NEW YORK, Y., ASSIGNOR TO NATIONAL CARBON COMPANY, INC, A CORPORATION OF NEW' YORK.

ELECTRICAL APPARATUS AND CORE THEREFOR.

Application filed February 18, 1.921.

This invention relates ratus, and particularly t trical transformer and to electrical a-ppao an improved elecan improved core formers adapted for use in conjunction with alternating cur-rent rectifiers, it will be understood thatthey mayalso be used advantageously in other ty paratus.

pes of electrical ap- Transformers generally, and especially the smaller enclosed types employed in alternating current rectifiers of battery charging outfits, develop considerable heat which, if not sufiiciently] dissipated, may injure the windings of the transformer.

An importantobject of this invention is,

therefore, to provide a transformer having an improved type of core in which the heat developed maybeeffec-tively dissipated to prevent injurious heating of-the transformer winding. Another object is to provide a transformer that may b e economically: constructed and one in which a port-ion or all of the flux set up in the main core may be conducted through an external circuit of magnetic material to improve its efficiency.

Broadly speaking, th obtained by providing ese objects may be a transformer, the

core of which comprises a hollow central leg having radially disposed yokes secured thereto.

Such yokes may form magnetic links between the opposite ends of the central leg and also constitute heat radiating fins.

The above and other 0 bjects andthe novel embodying this invention,

Fig. 2 is a side elevation of the same, Fig. 3 1s along1tud1nal sectional View of r the same taken on the line 33 of Fig. 1,

Fig. 4 isfia perspective view of the main leg of the transformer core, the same being slightly unwound to show the construct on thereof,

Fig. 5 is a plan view of the transformer,

with the yokes and clamping rings therefor rerneved, v,

Figs. 6 and 6 are sid see at the relies,

e and end views at Serial No. 446,128.

.of the transformer core.

Generally speaking, the transformer comprises an improved core having a'main leg C and auxiliary legs or, yokes Y which are secured to and disposed radially relatively to the axis of the main leg. The yokes Y have portions thereof-spaced from a surface of the main leg C providing an inter- Y vening space to receive the transformer primary and secondary windings P and S. The yokes contact with the surface of the leg C to conduct heat from the latter and accordinglyconstitute heat radiating fins as well as external magneticlinksto complete the magnetic circuit between the opposite ends of the main core leg C- As illustrated, the main leg- C comprises a hollow centrally disposed laminated unitary body of magnetic material, and is desirably formed by spirally winding a strip of magnetic material T upon a suitable mandrel, the inner end of such strip being temporarily secured as, by a hook portion H to a suitable part of the mandrel. The outer end of the strip T is cut away along 85, opposite parallel edges thereof, as shown, providing inwardly oifsetedges T and T", which form exterior shoulders on the leg C when the end-of the strip T is completely wound on. The shoulders T and T" provide abutment-s for the insulating annular cheek plates A and B. The primary winding P is wound on or otherwise applied to the exterior of the core C" between the shoulders T and T and the secondary'es winding is wound about or otherwise applied about the exterior of the primary winding, the cheek plates A and B confining these windings at the ends thereof. The

windings P and S may be wound on forms,

ery circuit may be suitably connected to obtain the full secondary voltage of the transformer; In order to obtain intermediate secondary voltages from the transformer, suitable taps 1, 1 are provided to whichleads may be connected, as by soldering. Thus different fractions of the maximum secondary voltage may be obtained by connecting the delivery circuit to the secondary terminal post 8 and to the desired tap 1 or 1'. The secondary winding S consists of the necessary number of turns of wire or other conductor to give the desired secondary voltage, and the taps 1, l are desirably provided by forming loops in different turns of the wire and drawing such loops utwarclly to a sul'ficient length to render them accessible for connecting suitable leads thereto. The taps 1, 1 may thus be made without severing the conductor forming the secondary winding or producing tap, and enlargements on the winding proper. The taps l, 1' are desirably drawn through holes a in a check plate A where the insulation may be removed therefrom and the desired leads soldered or otherwise connected thereto.

The heat generated in the primary and secondary windings and in the central core leg G should be dissipated in order to avoid injurious heating of the winding. Such heat is in part carried away by the circulation of cooling medium, such as air, through the passage in the center of the hollow leg C. Heat dissipating fins are also desirably provided to conduct the heat from the central leg C and from the windings P and S outwardly to provide a.v greater cooling surface accessible to the cooling medium circulated about the exterior oi. the transformer. As illustrated. suitable fins are provided in the form oi U-shaped yoltes Y which are secured to the central C and extend outwardly radially relatively to the axis of the core leg C. The U-shaped yokes Y are desirably stamped from sheet metal and have parallel limbs 3 the ends of which contact with the outer surface oi the central leg C above and below the annular cheek plates A and B, which latter bear against the inner sides of these limbs and space the windings therefrom. The yoke plates Y may be arranged in groups to form laminated yokes or fins, and in order to, increase the contacting and heat conducting surfaceengagement between the central leg C and these yokes, the outside yoke plates of each group may be provided with laterally extending portions or feet 7', as best shown in Figs. 1, 6, and 6 adapted to bear against the outer surface of the central leg C. The yoke plates have. portions 7/ intermediate the limbs 1 thereof. which fit into notches b in the peripheries of the cheek plates A and B and'bear against the outer or secondary winding S to conduct or radiate heat therefrom. The intermediate portions of the outer laminae 0t each group of yokes may have laterally projecting wings 1 formed integrally therewith and arranged to bear against the outer winding S to provide a greater surface of contact, whereby heat will be more readily conducted from the windings.

The yokes or fins Y are held in assembled relation on the central leg C by insulating end rings D and E which engage against the shoulders formed by oti'sct projections on the limbs 1 and clamp the ends of the limbs against the outer surface of the central leg to provide a substantially uninterrupted good heat-conducting path between the central leg and the yokes. The end rings D and E may be held in position by any suitable means. Screws 11 having the heads thereof counterset in holes 12 in the plates A and B project outwardly through holes 13 in the rings D and E and receive clamping nuts 14 on their outer ends to secure the parts together.

It will be understood that the central core leg C and the yokes Y are desirably o't magnetizable material, whereby the yokes serve as external magnetic links between the ends of the central leg- C, providing a very etlicient transformer structure. For certain purposes some or all ofthe yolres Y, or some or all of the yoke plates in each group of laminated yokes, may consist of non-magnetic material, such as brass, which will act as heat dissipating fins. In such apparatus, the yolres may be designed to carry only a portion of the magnetic flux set up m the core leg by the magnetizing winding 1, the magnetic circuit thus formed becoming saturated under load and nusing a certain amount of leakage magnetic flux.

The check rings A, B and the end clamp ing rings D, E, may be made ol metal. Such rings are illustrated al A and D in Figs. 7 and 8 and are similar to the rings A and D except that suitable slots 15 and 16, respectively, are cut transversely therethrough so that shot circuited secondary currents will not be induced therein. In order that the interior of the core shall more readily radiate heat, a suitable spider B may be inserted into the hollow core leg 0. As illustrated in Figs. 1. 9. ll) and 11. this spider may consist of two similar plates R provided with central longitudinal slots R" extending only part way into the strips so that they may be interfitted in intersecting relation with one another and held to gether as shown in Fig. 9. lVhen in position, as shown in Figs. 1 and 3, the outer edges of the plates R engage against the inner wall of the core leg C and conduct heat away therefrom so that such heat may be more readily dissipated by the air pass- Ell) lll)

ing through the core. This spider is, however, not essential to the operation of the transformer.

As previously indicated, certain novel features of this invention may be advantageously employedin othertypes of electrical apparatus and therefore, the application thereof is not limited to electrical transformers. The type of transformer illustrated is particularly suitable forwuse in combination with alternating curent rectifying apparatus, the hollow central core G being adapted to receive the vibrator of such rectifier, substantially in the axis thereof, in a manner similar to that disclosed in application Serial No; 432,020, filed in my name on December 20, 1920. Inemploying the herein disclosed type of transformer in a rectifier of the'above type, the spider R may of course be omitted, and the yokes are designed to provide heat radiating surface as well as an external magnetic circuit that will only allow a part of the flux set up in the central leg to pass therethrough.

Suflicient leakage magnetic flux may thus be provided to operate the vibrator that is disposed within and in the axis of the hollow central leg. Moreover, in some types of apparatus, the arrangement of the parts may be reversed and the passage in the hollow cylindrical legmay be made of such diameter as to accommodate the yokes and the windings therein, as well as a vibrator.

lVhile the invention is shown and described in detail, it will be understood that various features thereof may be modified without sacrificing any of the advantages thereof, and therefore it is to be understood that the invention is not limited to the exact construction disclosed.

I claim: I

1. In electrical apparatus, in combination, a core comprising a hollow central unitaryleg, and yokes secured thereto and disposed radially relatively to the axis of said leg, and an electrical winding disposed between portions of said yokes and said leg.

2. In electrical apparatus, in combination, a core comprising a laminated hollow central leg comprising a spirally wound strip of magnetizable material, and yokes secured to said central leg and radiating therefrom, said yokes having portions spaced from said leg to provide an intervening space, and an electrical winding in said space.

3. In an electrical transformer, in combination, a core comprising a central unitary leg, yokes extending radially from the axis of said leg, means for securing said yokes to said leg, and a transformer winding between said leg and portions of said yokes.

4. In an electrical transformenin combination, a core comprising a hollow cylindrical leg, yokes disposed radially relatively to the axis of said leg, and rings for clamptions.

to said le ing the opposite ends of said yokes to said leg, and an electrical winding between said leg and portions of said yokes.

5. An electrlcal transformer comprising in combination a core having a hollow cyengaging said leg and intermediate portions being spaced from the outer surface thereof, and means for securing said yokes to said leg, and transformer windings in the spaces between'said leg and such intermediate por- 6. An electrical transformer comprising in combination a. central leg, yokes engaging said central leg and having portions spaced therefrom, means for clamping said yokes a transformer winding between said leg and said portions of said yokes, and spacers between said winding and said yokes. 7

7. In electrical apparatus, in combination, a core comprising a main leg having spaced shoulders, yokes having end portions engaging said leg outside said shoulders and having intermediate portions spaced from said leg, and means for clamping said end portions to said leg, a winding between said shoulders and between said leg and said intermediate portions of the yokes, and

'means for confining said windings, such confining means bearing'against said shoulders and said yokes having such clamping means secured thereto.

8. A11 electrical transformer comprising, in combination, a hollow central leg, U- shaped yokes having feet engaging said leg and having portions spaced therefrom,

rings for clamping said yokes to said leg,

a transformer winding between said legand said portions of said yokes, annularplates between said winding and said yokes, and means for securing said rings to said plates.

9. Electrical apparatus comprising coaxial primary and secondary windings, a magnetizable core coaxial with said windings, and magnetic material cooperating with said core to provide a closed magnetic circuit, said magnetic material having a flux carrying capacity substantially less than that of said core, whereby a leakage flux is produced after said circuit becomes saturated.

10. In electrical apparatus, the combination with a magnetizable hollow unitary 1 core leg, of heat-dissipating yokes secured thereto and arranged radially relatively to the aXis of said leg.

11, In electrical appa 'atus, the combination with a magnetizable core leg, of heatdissipating yokes secured thereto and ra dially disposed relatively to said leg, said yokes comprising non-magnetic material.

12. In electrical apparatus, the combina- I tion with a magnetizable hollow unitary core leg, of heat-dissipating yokes secured thereto and radially disposed relatively to the axis of said leg, certain of said yokes comprising non-magnetic material.

18.. A core for electrical apparatus comprising, in combination, a hollow unitary leg and Yokes secured thereto and having portions spaced therefrom to form a space between said hollow leg. and said yokes to receive an electrical winding.

14-. A core for electrical apparatus comprising, in combination, a laminated hollow cylindrical unitary leg and radially disposed laminated yokes secured thereto and having portions thereof spaced from a surface of said hollow leg to provide an intervening space adapted to receive an electrical winding.

15. A core for electrical apparatus comprising, in combination, a substantially cent :11 unitary leg substantially U-shaped yokes extending outwardly therefrom. and means for securing, such yolres to said leg.

16. A magnetizable core for electrical apparatus comprising, in combination, a hollow substantially central unitary leg and yokes extending outwardly therefrom- 17. Av transformer core comprising in combination, a laminated magnetizablecentral unitary leg and yok-es secured thereto and radiating therefrom, said yokes having portions spaced from: the exterior surface of said central leg adapted to providea space to receive a transformer winding.

18. A core for electrical apparatus comprising in combination a. magnetizable leg, radially disposed yokes, and means comprisingrings for securing said yokes to said leg.

19. A core for electrical apparatus com prising in combination a hollow magnetizable' leg, radially disposed U-shaped yokes, and rings securing said yokes to said leg.

20. A core for electrical apparatus comprising in combination a magnetizable leg,

radially disposed U-shaped yokes having feet engagin a surface of said leg, and rings securing said yokes to said leg and clamping said feet against said surface.

21. A. core for electrical apparatus comprising in combination a main leg, and yokes secured to and arranged radially relatively to the axis of said main leg and comprising foot portions having extended engagement with the surface of said main leg to conduct heat from the latter.

22. A core for electrical apparatus comprising in combination a main leg, and yokes comprising groups of laminati'ons secured thereto and arranged radially relatively to the axis of said main leg, the outer laminations of each group being provided with laterally extending foot portions having extended engagement with the surface of said main leg to conduct heat from the latter.

23. In a core for electrical apparatus, in combination, a laminated central leg comprising a spirally wound strip of magnet/in able material, and yokes secured thereto, portions of said yokes being spaced from said leg to provide an intervening space to receive a magnetizing winding.

2%. A core for electrical apparatus co1nprising a leg consisting of a spirally wound strip of magnetizable material, such strip having a portion at its outer end narrower than the main portion of the strip whereby an edge of said narrow portion forms a shoulder on the exterior of said leg.

25. A core for electrical apparatus comprising a legconsisting of a spirally wound strip of magnetizable material, such strip having portions along the opposite sides of the outer end thereof cut away leaving a narrow portion having edges providing shoulders on the exterior of said leg.

In testimony whereof, I affix my signature.

NEVIL MONROE HOPKINS. 

